@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

:root {
  --usdt-green: #26a17b;
  --usdt-green-dark: #1a7a5c;
  --usdt-green-light: #e6f7f2;
  --usdt-dark: #0d1117;
  --usdt-surface: #161b22;
  --usdt-surface-2: #1f2937;
  --usdt-border: rgba(38, 161, 123, 0.2);
  --usdt-border-strong: rgba(38, 161, 123, 0.5);
  --usdt-text: #e6edf3;
  --usdt-text-muted: #8b949e;
  --usdt-radius: 12px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: 'Inter', sans-serif;
  background-color: var(--usdt-dark);
  color: var(--usdt-text);
  min-height: 100vh;
}

/* ── Header ── */
.logo-header {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px 0 16px;
  width: 100%;
  border-bottom: 1px solid var(--usdt-border);
  background: var(--usdt-surface);
}

.logo-img {
  height: 36px;
  display: block;
  filter: brightness(0) invert(1);
}

/* ── Container ── */
.container {
  max-width: 520px;
  margin: 48px auto;
  padding: 40px;
  background: var(--usdt-surface);
  border: 1px solid var(--usdt-border);
  border-radius: var(--usdt-radius);
  box-shadow: 0 0 40px rgba(38, 161, 123, 0.08);
}

/* ── Heading ── */
h1 {
  font-size: 22px;
  font-weight: 600;
  color: var(--usdt-text);
  border-bottom: 1px solid var(--usdt-border);
  padding-bottom: 16px;
  text-align: center;
  margin-top: 0;
  margin-bottom: 28px;
  letter-spacing: -0.3px;
}

/* ── Label ── */
label {
  display: block;
  margin-top: 20px;
  font-weight: 500;
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  color: var(--usdt-text-muted);
  margin-bottom: 8px;
}

/* ── Input ── */
input[type="text"],
input[type="number"] {
  width: 100%;
  padding: 12px 16px;
  margin-top: 4px;
  background: var(--usdt-surface-2);
  border: 1px solid var(--usdt-border);
  border-radius: 8px;
  font-family: inherit;
  font-size: 15px;
  color: var(--usdt-text);
  transition: border-color 0.2s;
  outline: none;
}

input[type="text"]:focus,
input[type="number"]:focus {
  border-color: var(--usdt-green);
  box-shadow: 0 0 0 3px rgba(38, 161, 123, 0.15);
}

input[type="text"]::placeholder,
input[type="number"]::placeholder {
  color: var(--usdt-text-muted);
}

/* ── Button ── */
button,
.btn {
  display: block;
  margin: 28px auto 0;
  width: 100%;
  max-width: 100%;
  padding: 14px 24px;
  background: #155c43;
  color: #ffffff;
  border: none;
  border-radius: 8px;
  font-family: inherit;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.8px;
  text-transform: uppercase;
  cursor: pointer;
  transition: background 0.2s, transform 0.1s;
  text-decoration: none;
  text-align: center;
}

button:hover,
.btn:hover {
  background: #0f4230;
}

button:active,
.btn:active {
  transform: scale(0.99);
}

/* ── Slider ── */
.slider-container {
  margin-top: 20px;
}

.slider-label {
  display: flex;
  justify-content: space-between;
  font-size: 12px;
  color: var(--usdt-text-muted);
  margin-bottom: 6px;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--usdt-green);
}

.value-display {
  text-align: right;
  font-size: 13px;
  color: var(--usdt-green);
  margin-top: 4px;
  font-weight: 500;
}

/* ── SEO Section ── */
.seo-section {
  max-width: 720px;
  margin: 60px auto;
  padding: 0 20px;
  font-family: 'Inter', sans-serif;
  line-height: 1.7;
  color: var(--usdt-text-muted);
}

.seo-section h2,
.seo-section h3 {
  color: var(--usdt-text);
  font-weight: 600;
  margin-top: 36px;
  margin-bottom: 12px;
  font-size: 17px;
}

.seo-section p {
  margin-bottom: 16px;
  font-size: 14px;
}

.seo-section ul {
  padding-left: 20px;
  margin-bottom: 16px;
}

.seo-section ul li {
  margin-bottom: 6px;
  font-size: 14px;
  color: var(--usdt-text-muted);
}

.seo-section ul li::marker {
  color: var(--usdt-green);
}

.seo-section strong {
  color: var(--usdt-text);
}

/* ── Result box ── */
.result-box {
  margin-top: 20px;
  font-family: 'Inter', sans-serif;
  font-size: 15px;
  color: var(--usdt-text);
}

/* ── Info block ── */
.info-block {
  max-width: 520px;
  margin: 32px auto;
  padding: 20px 28px;
  background: var(--usdt-surface);
  border: 1px solid var(--usdt-border);
  border-radius: var(--usdt-radius);
  font-family: 'Inter', sans-serif;
}

.info-block .label {
  font-weight: 600;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  color: var(--usdt-text-muted);
  margin-bottom: 10px;
}

.info-block .value p {
  margin: 6px 0;
  font-size: 14px;
  color: var(--usdt-text-muted);
}

.info-block a {
  color: var(--usdt-green);
  text-decoration: none;
}

.info-block a:hover {
  text-decoration: underline;
}

/* ── Footer ── */
.footer {
  margin-top: 60px;
  font-size: 13px;
  text-align: center;
  color: var(--usdt-text-muted);
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
  font-family: 'Inter', sans-serif;
  padding-bottom: 40px;
}

/* ── Mobile ── */
@media (max-width: 600px) {
  .container {
    margin: 16px;
    padding: 24px 20px;
  }

  .seo-section {
    padding: 0 16px;
  }
}